Plasma generating apparatus and method for operating same

ABSTRACT

A plasma generating apparatus according to an embodiment of the present invention comprises: a pair of electrodes arranged in a dielectric discharge tube; an initial discharge induction coil module; and a main discharge induction coil module. The initial discharge induction coil module and the main discharge induction coil module are connected to an RF power source, and the RF power source provides RF power having different resonance frequencies to the initial discharge induction coil module and the main discharge induction coil module, respectively.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/973,994, filed Dec. 10, 2020 which is a continuation of and claimspriority to PCT/KR2019/018549 filed on Dec. 27, 2019, which claimspriorities to Korea Patent Application No. KR 10-2018-0173639 filed onDec. 31, 2018 and Korea Patent Application No. KR 10-2019-0172614 filedon Dec. 23, 2019, the entireties of which are both hereby incorporatedby reference.

TECHNICAL FIELD

The present disclosure relates to a plasma generating apparatus and,more particularly, to an inductively coupled plasma apparatus performingdischarging at atmospheric pressure or higher pressure.

BACKGROUND

In general, inductively coupled plasma is generated using a drivingfrequency of several MHz at a pressure of hundreds of millitorr (mTorr).However, since an inductive electric field is weak, it may be difficultto use inductively coupled plasma for discharging at atmosphericpressure or at high pressure of several Torr or higher. Accordingly, itis necessary to sufficiently increase the strength of an inducedelectric field and to provide an additional component for initialdischarge. Even when discharge at an atmospheric pressure is maintained,the discharge may not be performed for a long period of time due tothermal damage caused by ions from plasma of a dielectric tube.

When inductively coupled plasma discharge is performed by applying RFpower to an induction coil surrounding a dielectric tube, the dielectrictube is heated by inductively coupled plasma to be damaged. Therefore,high-power inductively coupled plasma has a structural limitation.

In Korean Patent Registration No. 10-1657303, the present inventorsproposed swirl flow to maintain stability of plasma. However, an antennahaving a plurality of turns has an increase in an inducted electricfield during discharge and is limited in atmospheric pressure dischargebecause an antenna voltage accelerates ions to a tube wall to causethermal damage.

In Korean Patent Registration No. 10-1826883, the present inventorsproposed an inductively coupled plasma generator having a voltagedistribution structure in which a capacitor is inserted betweenantennas. According to Korean patent registration No. 10-1826883,initial discharge is inducted when a driving frequency does not satisfya resonance condition, but it is difficult to stably ignite atmosphericpressure discharge because intensity of an electric field is low.

SUMMARY

Example embodiments provide a plasma generating apparatus for generatingstable inductively coupled plasma at a near atmospheric pressure or at apressure of hundreds of Torr or higher.

An atmospheric-pressure plasma generating apparatus according to anexample embodiment may include a dielectric discharge tube; an initialdischarge induction coil module including an initial discharge inductioncoil surrounding the dielectric discharge tube, having a plurality ofturns, and generating atmospheric initial discharge and an initialdischarge capacitor connected to the initial discharge induction coil inseries to provide a first resonant frequency; a first electrode and asecond electrode, respectively disposed above and below the initialdischarge induction coil to provide initial discharge seeds; a DC powersupply configured to apply a DC high voltage between the first electrodeand the second electrode; a main discharge induction coil module havinga second resonant frequency and receiving initial discharge, generatedby the initial discharge induction coil module, to generate maininductively coupled plasma; and an RF power supply configured to supplyRF power to the initial discharge induction coil module and the maindischarge induction coil connected in parallel. The main dischargeinduction coil includes a plurality of unit antennas disposed to bespaced apart from the initial discharge induction coil and respectivelydisposed on a plurality of placement planes perpendicular to a centralaxis of the dielectric discharge tube; a first main capacitor and asecond main capacitor, respectively disposed on both ends of the unitantennas; and auxiliary capacitors, respectively connected to the unitantennas in series. The RF power induces initial discharge to theinitial discharge induction coil at the first resonant frequency withthe help of the DC high voltage. The RF power changes the drivingfrequency from the first resonant frequency to the second resonantfrequency to perform main discharge.

In an example embodiment, the atmospheric-pressure plasma generatingapparatus may further include a first detection sensor configured todetect a voltage or current flowing through the initial dischargeinduction coil. The RF power supply may detect a transition from acapacitively coupled mode to an inductively coupled mode using an outputof the first detection sensor, and may change a driving frequency fromthe first resonant frequency to the second resonant frequency.

In an example embodiment, the first electrode may be disposed above theinitial discharge induction coil and may be charged with a positive DChigh voltage. The second electrode may be disposed below the initialdischarge induction coil, may have a C shape to surround the dielectricdischarge tube, and may be charged with a negative DC high voltage.

In an example embodiment, the DC power supply may include an AC-DCconverter configured to convert commercial power into a DC voltage; ahigh-voltage pulse generator receiving the DC voltage to generate apositive DC high-voltage pulse and a negative DC high-voltage pulse; anda controller configured to control the high-voltage pulse generator.

In an example embodiment, the high-voltage pulse generator may include afirst transformer including a primary coil configured to receive the DCvoltage of the AC-DC converter and a secondary coil configured togenerate a positive DC high-voltage pulse; a first power transistorconnected to the primary coil of the first transformer; a secondtransformer including a primary coil configured to receive the DCvoltage of the AC-DC converter and a second coil configured to generatea negative DC high-voltage pulse; and a second power transistorconnected to the primary coil of the second transformer. The controllermay control gates of the first power transistor and the second powertransistors. One end of the secondary coil of the first transformer mayoutput a positive DC high-voltage pulse, and the other end of thesecondary coil of the first transformer may be grounded. One end of thesecondary coil of the second transformer may output a negative DChigh-voltage pulse, and the other end of the secondary coil of thesecond transformer may be grounded.

In an example embodiment, the initial discharge induction coil may be inthe form of a solenoid and may be wound in a plurality of layers.

In an example embodiment, the initial discharge induction coil may havea triple structure including an internal solenoid coil, an intermediatesolenoid coil, and an external solenoid coil.

In an example embodiment, the initial discharge capacitor may bedisposed on each of both ends of the initial discharge induction coil.

In an example embodiment, a coil constituting the unit antenna may havea rectangular cross section.

In an example embodiment, the unit antenna may include: the unit antennamay include: a first antenna disposed to be in contact with thedielectric discharge tube on a placement plane, perpendicular to acentral axis, and configured to form a loop; a second antenna disposedto surround the first antenna and configured to form a loop; and a thirdantenna disposed to surround the second antenna and configured to form aloop.

In an example embodiment, the unit antennas may be disposed on differentplacement planes, and the number of the unit antennas may be ten.

In an example embodiment, the unit antennas may be divided into a firstgroup, including five unit antennas, and a second group including theother five unit antennas. The unit antennas constituting the first groupmay be disposed at intervals of 72 degrees in an azimuthal direction,and the unit antennas constituting the second group may be disposed atintervals of 72 degrees in the azimuthal direction.

In an example embodiment, the unit antenna may include a plurality ofturns disposed on the same placement plane and may further include a

-shaped insulating spacer insulating the plurality of turns.

In an example embodiment, the first resonant frequency and the secondresonant frequency may be spaced apart from each other by 0.2 MHz ormore.

In an example embodiment, the first resonant frequency may be higherthan the second resonant frequency.

In an example embodiment, capacitance of the first main capacitor may bethe same as capacitance of the second main capacitor and may be twice ashigh as capacitance of the auxiliary capacitor.

In an example embodiment, a first voltage drop inducted to the initialdischarge induction coil at the first resonant frequency may be greaterthan a second voltage drop inducted to the unit antenna at the secondresonant frequency.

In an example embodiment, the sum of inductances of the unit antennasmay be greater than inductance of the initial discharge induction coil.

A method for operating atmospheric-pressure plasma generating apparatusaccording to an example embodiment includes: applying a DC high voltageto a first electrode and a second electrode, disposed to be spaced apartfrom each other, to provide initial discharge seeds to a dielectricdischarge tube; performing initial discharge by supplying AC power of afirst resonant frequency to an initial discharge induction coil moduleincluding an initial discharge induction coil surrounding the dielectricdischarge tube, having a plurality of turns, and generatingatmospheric-pressure initial discharge and an initial dischargecapacitor connected to the initial discharge induction coil in series toprovide the first resonant frequency; and inducing main inductivelycoupled plasma from the initial discharge by supplying AC power of asecond resonant frequency, different from the first resonant frequency,to a main discharge induction coil module connected to the initialdischarge induction coil module in parallel.

In an example embodiment, the method may further include: detectingcurrent flowing through the initial discharge induction coil or a dropof a voltage applied to both ends of the initial discharge inductioncoil. When the current flowing through the initial discharge inductioncoil or the drop of the voltage applied to both ends of the initialdischarge induction coil is greater than or equal to a threshold value,an RF power supply may change a driving frequency from the firstresonant frequency to the second resonant frequency to perform maindischarge in the unit antennas.

In an example embodiment, the main discharge induction coil module mayinclude: a plurality of unit antennas disposed to be spaced apart fromthe initial discharge induction coil, respectively disposed on aplurality of placement planes perpendicular to a central axis of thedielectric discharge tube, and connected in series; a first maincapacitor and a second main capacitor, respectively disposed on bothends of the unit antennas; and auxiliary capacitors connected betweenthe unit antennas in series. An RF power supply may induce initialdischarge to the initial discharge induction coil at the first resonantfrequency with the help of the DC high voltage. The RF power supply maychange a driving frequency from the first resonant frequency to thesecond resonant frequency to perform main discharge in the unitantennas.

A plasma generating apparatus according to an example embodimentincludes: a dielectric discharge tube; a seed charge generatorconfigured to generate seed charges in the dielectric discharge tube; aninitial discharge induction coil module including an initial dischargeinduction coil surrounding the dielectric discharge tube and receivingthe seed charges to generate initial discharge and a first impedancematching network connected to the initial discharge induction coil toprovide a first resonant frequency; a main discharge induction coilmodule including a plurality of unit antennas disposed to be spacedapart from the initial discharge induction coil, surrounding thedielectric discharge tube, and receiving the initial discharge togenerate main inductively coupled plasma and a second impedance matchingnetwork connected to the plurality of unit antennas to provide a secondresonant frequency; and an RF power supply configured to supply power tothe initial discharge induction coil module and the main dischargeinduction coil module.

In an example embodiment, the seed charge generator may include: a firstelectrode and a second electrode disposed on the dielectric dischargetube to provide seed charges; and a DC power supply configured to applya DC high voltage between the first electrode and the second electrode.

In an example embodiment, the first electrode may be disposed to be incontact with an external sidewall of the dielectric discharge tube, andthe second electrode may be disposed on a central axis of the dielectricdischarge tube and is electrically grounded.

In an example embodiment, the second electrode may be a nozzle forinjecting a gas.

In an example embodiment, the DC power supply may include: an AC-DCconverter configured to convert commercial AC power into a DC voltage; ahigh-voltage pulse generator receiving the DC voltage to generate atleast one of a positive DC high-voltage pulse and a negative DChigh-voltage pulse; and a controller configured to control thehigh-voltage pulse generator.

In an example embodiment, the high-voltage pulse generator may include:a first high-voltage pulse generator receiving the DC voltage togenerate a first high-voltage pulse; and a second high-voltage pulsegenerator receiving the DC voltage to generate a second high-voltagepulse.

In an example embodiment, the controller configured to control thehigh-voltage pulse generator may include: a first controller configuredto control the first high-voltage pulse generator; and a secondcontroller configured to control the second high-voltage pulsegenerator. The first high-voltage pulse may be applied to the firstelectrode, the second high-voltage pulse may be applied to the secondelectrode, and the first electrode and the second electrode may bedisposed on an external sidewall of the dielectric discharge tube to bespaced apart from each other.

In an example embodiment, the high-voltage pulse generator may include:a first transformer including a primary coil configured to receive theDC voltage of the AC-DC converter and a secondary coil configured togenerate a positive DC high-voltage pulse; a first power transistorconnected between a ground and the primary coil of the firsttransformer; a second transformer including a primary coil configured toreceive the DC voltage of the AC-DC converter and a secondary coilconfigured to generate a negative DC high-voltage pulse; and a secondpower transistor connected to a ground and the primary coil of thesecond transistor. The controller may control gates of the first powertransistor and the second power transistor. One end of the secondarycoil of the first transformer may output a positive DC high-voltagepulse, and the other end of the secondary coil of the first transformermay be grounded. One end of the secondary coil of the second transformermay output a negative DC high-voltage pulse, and the other end of thesecondary coil of the second transformer may be grounded.

In an example embodiment, the high-voltage pulse generator may include:a transformer including a primary coil configured to receive the DCvoltage of the AC-DC converter and a secondary coil configured to apositive DC high-voltage pulse; an inductor connected to the primarycoil of the transformer in parallel; a power transistor having one endgrounded, and connected to the primary coil of the transformer inseries; a resistor connected to the power transistor in parallel; acapacitor connected to the power transistor in parallel; and a diodedisposed between the resistor and the capacitor connected to the otherend of the power transistor in parallel. The controller may control agate of the power transistor. One end of the secondary coil of thetransformer may output a negative DC high-voltage pulse, and the otherend of the secondary coil of the transistor may be grounded.

In an example embodiment, the high-voltage pulse generator may include:a transformer including a primary coil configured to receive the DCvoltage of the AC-DC converter and a secondary coil configured togenerate a negative DC high voltage; an inductor connected to theprimary coil of the transformer in parallel; and a power transistorconnected between a ground and the primary coil of the transformer. Thecontroller may control a gate of the power transistor. On end of thesecondary coil of the transformer may output a negative DC high-voltagepulse, and the other end of the secondary coil of the transformer may begrounded.

In an example embodiment, the high-voltage pulse generator may include:a transformer including a primary coil configured to receive the DCvoltage of the AC-DC converter and a secondary coil configured togenerate a negative DC high-voltage pulse; an inductor connected to theprimary coil of the transformer in parallel; a power transistorconnected between a ground and the primary coil of the transformer inseries; a resistor and a capacitor, each having one end connected to theDC voltage of the AC-DC converter, connected to each other in parallel;and a diode having one end connected between the power transistor andthe primary coil and the other end connected to the other end of theresistor and the capacitor connected in parallel. The controller maycontrol a gate of the power transistor. One end of the secondary coil ofthe transformer may output a negative DC high-voltage pulse, and theother end of the secondary coil of the transformer may be grounded.

In an example embodiment, the high-voltage pulse generator may include:a transformer including a primary coil configured to receive the DCvoltage of the AC-DC converter and a secondary coil configured togenerate a positive DC high-voltage pulse; an inductor connected to theprimary coil of the transformer in parallel; a power transistorconnected between a ground and the primary coil of the transformer inseries; a resistor connected to the power transistor in parallel; acapacitor connected to the power transistor in parallel; and a diodedisposed between the resistor and the capacitor connected to the otherend of the power transistor in parallel. The primary coil and thesecondary coil may have a phase difference of 180 degrees. Thecontroller may control a gate of the power transistor. One end of thesecondary coil of the transformer may output a positive DC high-voltagepulse, and the other end of the secondary coil of the transformer may begrounded.

In an example embodiment, the first impedance matching network mayinclude an initial discharge capacitor connected to the initialdischarge induction coil in series.

In an example embodiment, the first impedance matching network mayinclude a pair of initial discharge capacitors, respectively connectedto both ends of the initial discharge induction coil.

In an example embodiment, the first impedance matching network mayinclude a transformer and a pair of initial discharge capacitors,respectively connected to both ends of the initial discharge inductorcoil. A primary coil of the transformer may be connected to an outputterminal of the RF power supply, and a secondary coil of the transformermay be connected to both ends of the initial discharge inductor coil andthe pair of initial discharge capacitors connected in series.

In an example embodiment, the first impedance matching network mayinclude: a first initial discharge capacitor connected to the initialdischarge induction coil in parallel; and a second initial dischargecapacitor and a third initial discharge capacitor, respectivelyconnected to both ends of the initial discharge capacitor and theinitial discharge induction coil connected in parallel.

In an example embodiment, in the main discharge inductor coil module,the plurality of unit antennas may be respectively disposed on aplurality of placemen plane, perpendicular to a central axis of thedielectric discharge tube, and are connected in series, auxiliarycapacitors may be connected between adjacent unit antennas in series,and the second impedance matching network may include a first capacitorand a second main capacitor, respectively connected to both ends of theunit antennas connected in series.

In an example embodiment, the RF power supply may include: a rectifierconfigured to convert commercial power into DC power; an inverterconfigured to receive the DC power and to converter the received DCpower into RF power; and a controller configured to control theswitching signals to control a driving frequency and power. The RF powersupply may operate at the first resonant frequency during initialdischarge and may operate at the second resonant frequency when maininductively coupled plasma is generated.

In an example embodiment, the RF power supply may include: a first RFpower supply configured to supply AC power to the initial dischargeinduction coil module and operating at the first resonant frequency; anda second RF power supply configured to supply AC power to the maindischarge induction coil module and operating at the second resonantfrequency. The first RF power supply may include: a first rectifierconfigured to convert AC power into DC power; a first inverterconfigured to receive DC power of the first rectifier and to supply ACpower of the first resonant frequency to the initial discharge inductioncoil module; and a first controller configured to control an output ofthe first inverter. The second RF power supply may include: a secondrectifier configured to convert AC power into DC power; a secondinverter configured to receive DC power of the second rectifier and tosupply AC power of the second of a second resonant frequency to the maindischarge induction coil module; and a second controller configured tocontrol an output of the second inverter.

In an example embodiment, the RF power supply may include: a rectifierconfigured to AC power into DC power; a first RF power supply configuredto receive DC power of the rectifier and to supply AC power to theinitial discharge induction coil module and operating at the firstresonant frequency; and a second RF power supply configured to receiveDC power of the rectifier and to supply AC power to the main dischargeinduction coil and operating at the second resonant frequency.

In an example embodiment, the first RF power supply may include: a firstinverter configured to receive DC power of the rectifier and to convertthe received DC power into first AC power of a first resonant frequency;a first controller configured to control the first inverter; a secondinverter configured to receive DC power of the rectifier and to convertthe received DC power into AC power of a second resonant frequency; anda second controller configured to control the second inverter.

In an example embodiment, the first RF power supply may operate within afrequency range from 4 MHz to 5 MHz, and the second RF power supply mayoperate within in a frequency range from 400 kHz to 4 MHz.

In an example embodiment, each of the first inverter and the secondinverter may have a full-bridge structure or a half-bridge structure.

In an example embodiment, the plasma generating apparatus may furtherinclude: a first detection sensor configured to detect current flowingthrough the initial discharge induction coil. The RF power supply maydetect a transition from a capacitively coupled mode to an inductivelycoupled mode using an output of the first detection sensor to change adriving frequency from the first resonant frequency to the secondresonant frequency.

In an example embodiment, the plasma generating apparatus may furtherinclude: a second detection sensor configured to detect current flowingthrough the main discharge induction coil module. The RF power supplymay detect that the main inductively coupled plasma is generated usingan output of the second detection sensor to interrupt power supplied tothe initial discharge induction coil module.

In an example embodiment, the first electrode may be disposed above theinitial discharge induction coil to be charged with a positive DC highvoltage, and the second electrode may be disposed below the initialdischarge induction coil, may have a C shape to surround the dielectricdischarge tube, and may be charged with a negative DC high voltage.

In an example embodiment, the initial discharge induction coil may be inthe form of a solenoid and may be wound in multiple layers.

In an example embodiment, the initial discharge induction coil may havea triple structure including an internal solenoid coil, an intermediatesolenoid coil, and an external solenoid coil.

In an example embodiment, the unit antenna may include: a first antennadisposed to be in contact with the dielectric discharge tube on aplacement plane, perpendicular to a central axis, and configured to forma loop; a second antenna disposed to surround the first antenna andconfigured to form a loop; and a third antenna disposed to surround thesecond antenna and configured to form a loop.

In an example embodiment, the unit antenna may include a plurality ofturns disposed on the same placement plane and may further include a

-shaped insulating spacer insulating the plurality of turns.

A method for operating a plasma generating apparatus according to anexample embodiment may include: injecting a first gas into a dielectricdischarge tube; providing seed charges to an inside of the dielectricdischarge tube using the first gas; performing initial discharge of thefirst gas from the seed charges with AC power of a first resonantfrequency using an initial discharge induction coil and a firstimpedance matching network connected to the initial discharge inductioncoil; and generating main inductively coupled plasma of the first gaswith AC power of a second resonant frequency, different from the firstresonant frequency, using a plurality of unit antennas and a secondimpedance matching network.

In an example embodiment, the method may further include: maintainingthe main inductively coupled plasma while changing the first gas into asecond gas.

In an example embodiment, after the initial discharge of the first gas,the method may further include: generating preliminary main inductivelycoupled plasma of the first gas from the initial discharge with AC powerof a frequency near a second resonant frequency using a plurality ofunit antennas and a second impedance matching network.

In an example embodiment, the method may further include: interruptingthe AC power of the first resonant frequency when the preliminary maininductively coupled plasma is generated.

BRIEF DESCRIPTION OF DRAWINGS

The above and other aspects, features, and advantages of the presentdisclosure will be more clearly understood from the following detaileddescription, taken in conjunction with the accompanying drawings.

FIG. 1 is a conceptual diagram illustrating an application example of anatmospheric-pressure plasma device according to an example embodiment ofthe present disclosure.

FIG. 2A is a conceptual diagram illustrating an initial dischargeoperation of an atmospheric pressure device according to an exampleembodiment of the present disclosure.

FIG. 2B is a conceptual diagram illustrating a main discharge operationof an atmospheric-pressure plasma device according to an exampleembodiment of the present disclosure.

FIG. 3 is a conceptual diagram illustrating the atmospheric pressure inFIG. 2A from a circuit point of view.

FIG. 4 is a conceptual diagram illustrating division of a voltageapplied to an initial discharge induction coil during an initialdischarge operation of the atmospheric-pressure plasma device in FIG.2A.

FIG. 5 is a conceptual diagram illustrating division of a voltageapplied to a main discharge induction coil during a main dischargeoperation of the atmospheric-pressure plasma device in FIG. 2A.

FIG. 6 is a plan view illustrating a disposition relationship of unitantennas of a main discharge induction coil module according to anexample embodiment of the present disclosure.

FIG. 7 is a plan view of unit antennas of a main discharge inductioncoil module according to an example embodiment of the presentdisclosure.

FIG. 8 is a cross-sectional view illustrating an insulating state ofunit antennas of a main discharge induction coil module according to anexample embodiment of the present disclosure.

FIG. 9 is a cutaway perspective view illustrating a dispositionrelationship of a first electrode and a second electrode according to anexample embodiment of the present disclosure.

FIG. 10 is a circuit diagram of a DC power supply according to anotherexample embodiment of the present disclosure.

FIG. 11 is a circuit diagram illustrating a high-voltage pulse generatorin FIG. 10.

FIG. 12 is a cross-sectional view illustrating a main dischargeinduction coil module of an atmospheric-pressure plasma generatingapparatus according to another example embodiment of the presentdisclosure.

FIG. 13 is a plan view illustrating a disposition relationship of unitantennas of the main discharge induction coil module in FIG. 12 .

FIG. 14 is an equivalent circuit diagram illustrating an initialdischarge mode of the atmospheric-pressure plasma generating apparatusin FIG. 12 .

FIG. 15 is an equivalent circuit diagram illustrating a main dischargemode of the atmospheric-pressure plasma generating apparatus in FIG. 12.

FIG. 16 is a timing diagram illustrating an initial discharge mode and amain discharge mode of the atmospheric-pressure plasma generatingapparatus in FIG. 12 .

FIG. 17 is a conceptual diagram illustrating a plasma generatingapparatus according to FIG. 2A.

FIG. 18 is a conceptual diagram illustrating a plasma generatingapparatus according to another example embodiment of the presentdisclosure.

FIG. 19 is a conceptual diagram illustrating a plasma generatingapparatus according to another example embodiment of the presentdisclosure.

FIG. 20 is a conceptual diagram illustrating discharge of the plasmagenerating apparatus in FIG. 19 .

FIG. 21 is a timing diagram of signals in FIG. 19 .

FIG. 22 is a flowchart illustrating a method for operating the plasmagenerating apparatus in FIG. 19 .

FIG. 23 is a conceptual diagram illustrating a plasma generatingapparatus according to another example embodiment of the presentdisclosure.

FIGS. 24 to 28 each illustrate an initial discharge induction coilmodule connected to a second RF power supply according to an exampleembodiment of the present disclosure.

FIG. 29 illustrates a main discharge induction coil module connected toa second RF power supply according to another example embodiment of thepresent disclosure.

FIG. 30 is a circuit diagram of a full-bridge inverter used in a firstinverter or a second inverter.

FIG. 31 is a circuit diagram of a half-bridge inverter according to anexample embodiment of the present disclosure.

FIG. 32 is a conceptual diagram illustrating a seed charge generatoraccording to another example embodiment of the present disclosure.

FIG. 33 to FIG. 36 are conceptual diagrams of a high-voltage pulsegeneration unit according to another example embodiment of the presentdisclosure.

FIG. 37 is a plan view of a unit antenna of a main discharge inductioncoil module according to another example embodiment of the presentdisclosure.

DETAILED DESCRIPTION

Hereinafter, example embodiments will be described with reference to theaccompanying drawings.

A plasma generator according to an example embodiment of the presentdisclosure includes a pair of electrodes disposed in a dielectricdischarge tube, an initial discharge induction coil module, and a maindischarge induction coil module. The initial discharge induction coilmodule and the main discharge induction coil module are connected to anRF power supply in parallel, and the RF power supply selectivelysupplies RF power to the initial discharge induction coil module or themain discharge induction coil module according to a resonant frequency.

The initial discharge module includes an antenna advantageous forignition, and the main discharge module has antenna characteristicsadvantageous for discharge maintenance. The initial discharge module andthe main discharge module, connected to each other in parallel, havedifferent impedance characteristics depending on a driving frequency.The initial discharge module has a first resonant frequency, and themain discharge module has a second resonant frequency. When currentflows at the first resonant frequency, the current mainly flows to theinitial discharge module. Since impedance is relatively high at thefirst resonant frequency in a route rather than resonance, a relativelysmall amount of current flows. When current flows at the second resonantfrequency, the current mainly flows to the main discharge module. Evenwhen there are three or more discharge modules, if different resonantfrequencies are allocated to the respective discharge modules, currentmay be supplied to a desired discharge module. Therefore, according tothe present disclosure, impedance matching may be performed in a wideactual resistance range, a wide discharge control range (a flow rate,power, and a pressure) may be implemented, and current may to beswitched to a multi-purposed discharge module to change a dischargefunction.

The pair of electrodes may be respectively disposed above and below theinitial discharge induction coil of the initial discharge module togenerate to apply a DC voltage at an atmospheric pressure to generate anelectrostatic vertical electric field E_ig in a direction of a centralaxis of the dielectric discharge tube for performing initial dischargeand to generate seed charges.

The initial discharge induction coil module is disposed between the pairof electrodes, and includes an initial discharge induction coil and aninitial discharge capacitor connected to the initial discharge inductioncoil in series. The main discharge module and the initial dischargemodule are connected in parallel. The initial discharge induction coilmodule has a first resonant frequency, and receives RF power having thefirst resonant frequency from the RF power supply in an initialdischarge mode to perform initial discharge. The main discharge moduledoes not perform discharge due to high impedance at the first resonantfrequency. Plasma, generated by the initial discharge induction coil,transitions from a capacitively coupled mode (or an E mode) to aninductively coupled mode (or an H mode). In the capacitively coupledmode (or the E mode), the initial discharge induction coil generates apotential difference on both ends of the initial discharge inductioncoil at the first resonant frequency. After the transition to theinductively coupled mode (or the H mode), actual plasma resistance isincreased and the first current, flowing to the initial dischargeinductor coil, is decreased.

The main discharge module includes serially connected unit antennasspaced apart from the initial discharge induction coil and respectivelydisposed on a plurality of placement planes, a first main capacitor anda second main capacitor respectively disposed both ends of the unitantennas, and an auxiliary capacitor connected between the unit antennasin series. The main discharge module and the initial discharge moduleare connected in parallel. The main discharge module has a secondresonant frequency. During a transition from the capacitively coupledmode (or the E mode) to the inductively coupled mode (or the H mode) dueto the initial discharge induction coil, the RF power supply changes adriving frequency from the first resonant frequency to the secondresonant frequency. At the same time, the DC voltage is removed from thepair of electrodes. Accordingly, the initial discharge module does notperform discharge because current does not flow due to high impedance,and the main discharge module allows current to flow due to lowimpedance and stably generates inductively coupled plasma.

Hereinafter, the present disclosure will be described in more detailbased on preferred embodiments. However, these embodiments are forbetter understanding of the present disclosure, and it is obvious tothose skilled in the art that the scope of the present disclosure is notlimited thereto. In addition, in the case in which detailed descriptionof known functions or configurations in relation to the presentdisclosure is judged as unnecessarily making the essence of the presentdisclosure vague, the detailed description will be excluded.

FIG. 1 is a conceptual diagram illustrating an application example of anatmospheric-pressure plasma device according to an example embodiment ofthe present disclosure.

Referring to FIG. 1 , a substrate processing apparatus 10 may include asubstrate holder 93 provided inside of a vacuum container 92, and mayperform a deposition process, an etching process, a diffusion process,or an ion implantation process on a substrate 94 disposed on thesubstrate holder 93. The vacuum container 92 is exhausted by a vacuumpump 95, and an exhaust gas is purified through an atmospheric-pressureplasma generation device 100 to be discharged to an external entity. Theexhaust gas includes contaminants such as fine particles, deadly toxicgases, and greenhouse gases.

The exhaust gas is discharged after being purified through a gasscrubber. The gas scrubber includes a combustion-type gas scrubber or aplasma-type gas scrubber.

An atmospheric pressure discharge plasma method may include ahigh-voltage flat-type plasma method, an arc torch method, and aninduction heating plasma method. The high-voltage flat-type plasmamethod has high discharge maintenance, but encounters difficulty inestablish low plasma density and high temperature conditions at a highoperating pressure. Therefore, an effect of removing toxic substances bythermochemical decomposition is low.

High-temperature plasma such as an arc torch provides a high reactiontemperature, but exhibits low decomposition efficiency because a processgas is not directly injected into the plasma and low durability of anelectrode for generating an arc.

An atmospheric-pressure plasma device according to an example embodimentmay implement high plasma density (10¹⁶/cm³) and high gas temperature(3000 degrees Celsius) at a pressure of 100 Torr or more usinginductively coupled plasma. Accordingly, the atmospheric-pressure plasmadevice may be disposed in back of a vacuum pump to decompose and processa noxious gas flowing after being mixed with a gas of several tens ofstandard liter per minute (SLM) or more under atmospheric pressure. Thenoxious gas may be a C_(x)F_(y) or S_(x)F_(y) gas. In the presentdisclosure, inductively coupled discharge of a C_(x)F_(y) gas, which isconventionally difficult to be discharged at atmospheric pressure, maybe performed at the atmospheric pressure. An atmospheric pressure faccording to an example embodiment may be used in a process such as CO₂reforming.

FIG. 2A is a conceptual diagram illustrating an initial dischargeoperation of an atmospheric pressure device according to an exampleembodiment of the present disclosure.

FIG. 2B is a conceptual diagram illustrating a main discharge operationof an atmospheric-pressure plasma device according to an exampleembodiment of the present disclosure.

FIG. 3 is a conceptual diagram illustrating the atmospheric pressure inFIG. 2A from a circuit point of view.

FIG. 4 is a conceptual diagram illustrating division of a voltageapplied to an initial discharge induction coil during an initialdischarge operation of the atmospheric-pressure plasma device FIG. 2A.

FIG. 5 is a conceptual diagram illustrating division of a voltageapplied to a main discharge induction coil during a main dischargeoperation of the atmospheric-pressure plasma device in FIG. 2A.

FIG. 6 is a plan view illustrating a disposition relationship of unitantennas of a main discharge induction coil module according to anexample embodiment of the present disclosure.

FIG. 7 is a plan view of unit antennas of a main discharge inductioncoil module according to an example embodiment of the presentdisclosure.

FIG. 8 is a cross-sectional view illustrating an insulating state ofunit antennas of a main discharge induction coil module according to anexample embodiment of the present disclosure.

FIG. 9 is a cutaway perspective view illustrating a dispositionrelationship of a first electrode and a second electrode according to anexample embodiment of the present disclosure.

Referring to FIGS. 2 to 9 , an atmospheric-pressure plasma generatingapparatus 100 may include a dielectric discharge tube 140; an initialdischarge induction coil module 102 including an initial dischargeinduction coil 120 surrounding the dielectric discharge tube 140, havinga plurality of turns, and generating atmospheric-pressure initialdischarge and initial discharge capacitors 122 a and 122 b connected tothe initial discharge induction coil 120 in series to provide a firstresonant frequency fa; a first electrode 114 and a second electrode 116disposed above and below the initial discharge induction coil 120 toprovide initial discharge seeds; a DC power supply 112 configured toapply a DC high voltage between the first electrode 114 and the secondelectrode 116; a main discharge induction coil module 103 having asecond resonant frequency fb and configured to receive the initialdischarge generated by the initial discharge induction coil 102 togenerate main inductively coupled plasma; and an RF power supply 150configured to supply RF power to the initial discharge induction coilmodule 102 and the main discharge induction coil module 103 connected inparallel and to change a driving frequency.

The main discharge induction coil module 103 includes a plurality ofunit antennas 132 disposed to be spaced apart from the initial dischargeinduction coil 120, respectively disposed on a plurality of placementplanes perpendicular to a central axis of the dielectric discharge tube140, and connected to each other in series; a first main capacitor 133 aand a second main capacitor 133 b, respectively disposed on both ends ofthe unit antennas 132; and auxiliary capacitors 134 connected to eachother between the unit antennas 132 in series.

The RF power supply 150 induces initial discharge to the initialdischarge induction coil 120 at the first resonant frequency fa with thehelp of the DC high voltage. The RF power supply 150 changes the drivingfrequency from the first resonance frequency fa to the second resonancefrequency fb to perform main discharge.

Due to a low inducted electric field, it may be difficult foratmospheric pressure inductively coupled plasma to generate ignition (orinitial discharge). Therefore, a help of DC discharge performed by thefirst electrode 114 and the second electrode 116 is given to achievestable initial discharge. On the other hand, it may be difficult for DCdischarge to form high plasma density. An electrode, disposed outside ofthe dielectric discharge tube 140, causes the dielectric discharge tube140 to be damaged by a high electric field E_ig.

The initial discharge induction coil 120 generates initial inductivelycoupled plasma with the help of seed charges generated by DC discharge.To this end, a strong electrostatic vertical electric field E_z in adirection of the central axis of the dielectric discharge tube 140 isrequired. The strong electrostatic vertical electric field E_z dependson a structure of the initial discharge induction coil. Theelectrostatic vertical electric field E_z of the initial dischargeinduction coil 120 may establish a capacitively coupled mode. Theelectrostatic vertical electric field E_z may be generated by a highpotential difference Va applied to both ends of the initial dischargeinduction coil. The electrostatic vertical electric field E_z may be inproportion to inductance La of the initial discharge induction coil 120.However, when the inductance La of the initial discharge induction coil120 is excessively high, the power of the RF power supply 150 is notefficiently transferred to a load (an initial discharge induction coil)due to high impedance. Therefore, the initial discharge capacitors 122 aand 122 b are connected the initial discharge induction coil 120 inseries to provide the first resonant frequency fa. When the RF powersupply 150 operates at the first resonant frequency fa, an imaginarypart of impedance Za viewed from an output terminal of the RF powersupply toward the initial discharge induction coil 120 may be removed.Accordingly, the RF power supply 150 may stably transfer RF power to theinitial discharge induction coil. In addition, since the initialdischarge induction coil 120 has high inductance, a high potentialdifference Va may be induced to both ends of the initial dischargeinduction coil 120, and thus, the electrostatic vertical electric fieldE_z may establish the capacitively coupled mode. In the capacitivelycoupled mode, streamer discharge is locally performed in a direction ofthe central axis of the dielectric discharge tube 140.

When plasma is sufficiently generated by the capacitively coupled mode,an induced electric field E_a_ind in an azimuthal direction is generatedby first current Ia flowing through the initial discharge induction coil120. Due to the induced electric field E_a_ind, plasma transitions froma capacitively coupled mode to an inductively coupled mode. In theinductively coupled mode established by the initial discharge inductioncoil 120, plasma is generated overall in the dielectric discharge tube140. In the inductively coupled mode, the first current Ia flowingthrough the initial discharge induction coil and the potentialdifference Va applied to both ends of the initial discharge inductioncoil are decreased, as compared with those in the capacitively coupledmode.

However, in the inductively coupled mode established by the initialdischarge induction coil 120, the high inductance La of the initialdischarge induction coil 120 allows a high potential difference to bestill maintained at both ends of the initial discharge induction coil.Accordingly, a plasma sheath is formed between plasma having constantplasma potential and the initial discharge induction coil 120, and ionsare accelerated to an internal wall of the dielectric discharge tube 120through the plasma sheath. Thus, the dielectric discharge tube 120 isdamaged by heat and discharge efficiency is reduced.

In the present disclosure, the initial discharge induction coil 120optimized for initial discharge and the main discharge induction coilmodule 103 for suppressing thermal damage of the dielectric dischargetube 140 and increasing the discharge efficiency are used to address theabove issues. In an initial discharging step, RF power is introducedinto the initial discharging induction coil 120 to from a transitionfrom a capacitively coupled mode to an inductively coupled mode. Themain discharge induction coil module 103 may directly generate plasma inthe inductively coupled mode without entering the capacitively coupledmode using a large amount of charged particles generated by the initialdischarge induction coil 120.

The main discharge induction coil module 103 has electricalcharacteristics and discharge characteristics different from those ofthe initial discharge induction coil module 102. The main dischargeinduction coil module 103 includes a plurality of unit antennas 132constituting the main discharge induction coil module. The antennas 132are disposed on different placement planes to be stacked on each other,and are disposed to surround the dielectric discharge tube 140.

It may be difficult for the main discharge induction coil module 103 tooperate solely without the initial discharge induction coil. However,after the initial discharge induction coil transitions to theinductively coupled mode, second current Ib flows to the main dischargeinduction coil module 103 at the same time as the first current Iaflowing through the initial discharge induction coil 120 is removed. Themain discharge induction coil module 103 may perform stable discharge inthe inductively coupled mode immediately without entering thecapacitively coupled mode. Due to voltage division, a second potentialdifference Vb applied to each of the unit antennas 132 is less than thepotential difference Va applied to both ends of the initial dischargeinduction coil 120. The sum Lb of inductances of the unit antennas 132is larger than the inductance La of the initial discharge induction coil120. Therefore, intensity of the induced electric field E_b_ind is highand a potential difference of the plasma sheath is small, so thatthermal breakage of the dielectric discharge tube 140 is suppressed anddischarge efficiency is increased.

The main discharge induction coil module 103 includes a plurality ofunit antennas 132 disposed to be spaced apart from the initial dischargeinduction coil, respectively disposed on placement planes perpendicularto a central axis of the dielectric discharge tube 140, and connected toeach other in series; a first main capacitor 133 a and a second maincapacitor 133 b, respectively disposed on both ends of the unit antennas132; and auxiliary capacitors 134 connected between the unit antennas132 in series. The main discharge induction coil module 103 has a secondresonant frequency fb and performs voltage division in proportion to thenumber of the unit antennas 132. Thus, thermal damage to the dielectricdischarge tube 140 is suppressed and discharge efficiency is increased.

The RF power supply 150 may change a driving frequency and mayselectively supply RF power to the initial discharge induction coilmodule 102 and the main discharge induction coil module 103 connected toeach other in parallel. The RF power supply 150 mainly supplies power tothe initial discharge induction coil module 102 at the first resonantfrequency fa. On the other hand, the RF power supply 150 mainly suppliespower to the main discharge induction coil module 103 at the secondresonance frequency fb.

The dielectric discharge tube 140 may be a cylindrical dielectricdischarge tube. Specifically, a material of the dielectric dischargetube 140 may be ceramic, sapphire, or quartz. The ceramic may be aluminaor AlN. An external diameter of the dielectric discharge tube 140 may beseveral centimeters to tens of centimeters. An internal diameter of thedielectric discharge tube 140 may be several millimeters to tens ofmillimeters smaller than the external diameter thereof. A length of thedielectric discharge tube 140 may be several centimeters to severalmeters. Both ends of the dielectric discharge tube 140 may berespectively coupled to an upper flange 142 and a lower flange 144 to besealed. The lower flange 144 may receive an exhaust gas of the substrateprocessing apparatus 10 as a process gas.

Referring to FIG. 9 , the initial discharge induction coil 120 maysignificantly decrease the number of turns per unit length in a lengthdirection of the dielectric discharge tube 120. The initial dischargeinduction coil 120 may be a solenoid coil having a multilayer structure.Specifically, the initial discharge induction coil 120 has a solenoidshape and may be wound in multiple layers. The initial dischargeinduction coil 120 may have a triple-layer structure including aninternal solenoid coil 120 a, an intermediate solenoid coil 120 b, andan external solenoid coil 120 c. The internal solenoid coil 120 a may befour turns surrounding the dielectric discharge tube 120. Theintermediate solenoid coil 120 b may be four turns surrounding theinternal solenoid coil 120 a. The external solenoid coil 120 c may bethree turns surrounding the intermediate solenoid coil 120 b. Theinitial discharge induction coil 120 may be wound to constructivelyinterfere with a magnetic field therein. For example, the inductance Laof the initial discharge induction coil 120 may be 8 uH. The initialdischarge induction coil 120 may include a copper pipe, and a coolantmay flow inside the initial discharge induction coil. A cross section ofa pipe, constituting the initial discharge induction coil, may have acircular shape.

The initial discharge capacitors 122 a and 122 b may be connected to atleast one of both ends of the initial discharge induction coil. Theinitial discharge capacitors 122 a and 122 b and the initial dischargeinduction coil 120 may be connected in series to provide the firstresonant frequency fa. Capacitance Ca of the first initial dischargecapacitor 122 a may be the same as capacitance Ca of the second initialdischarge capacitor 122 b.

The first resonant frequency fa may be 3.3 MHz. The first resonancefrequency fa may be defined by equivalent capacitance C′a of the initialdischarge capacitors 122 a and 122 b and inductance La of the initialdischarge induction coil 120. The initial discharge capacitors 122 a and122 b may be disposed on one of both ends of the initial dischargeinduction coil.

The DC power supply 112 may generate a high-voltage DC pulse. Thehigh-voltage DC pulse may be a negative DC high voltage and a positiveDC high voltage. The DC power supply 112 may generate a high-voltagepulse of several tens of kilohertz (kHz). The negative DC high voltagemay be negative tens of kilovolts (kV), and the positive DC high voltagemay be positive tens of kV.

A pair of electrodes 114 and 116 may include a first electrode 114 and asecond electrode 116, respectively disposed above and below the initialdischarge induction coil 120. The first electrode 114 may be chargedwith a positive DC high voltage and may be in the form of a rectangularplate adhering and attached to the dielectric discharge tube 140.

The first electrode 114 is disposed to be in contact with an externalsidewall of the dielectric discharge tube 140 above the initialdischarge induction coil 120 and receives the positive DC high voltage.The first electrode 114 may have a rectangular shape.

The second electrode 116 is disposed to be in contact with an externalsidewall of the dielectric discharge tube 120 below the initialdischarge induction coil 120 and receives the negative DC high voltage.The second electrode 116 may have a “C” shape to surround the dielectricdischarge tube 140. The second electrode 116 may have a larger area thanthe first electrode to generate electrons. The second electrode 116 maybe a band-shaped conductor disposed to surround the dielectric dischargetube 140. The second electrode 116 may be heated by an inductionelectric field E_a_ind generated by the initial discharge induction coilor an induction electric field E_b_ind generated by the unit antennas.Therefore, the second electrode 116 may have a “C” shape without forminga perfect loop such that eddy current, generated by the induced electricfields E_a_ind and E_b_ind, does not flow. The second electrode may becharged with a negative DC high voltage and may be in the form of a bandadhering and attached to the dielectric discharge tube 140. In addition,the second electrode 116 may be formed to be serpentine such that theinduced electric field in an azimuthal direction does not flow, or mayinclude a plurality of slits extending in a direction of a central axisof a cylinder.

Voltages, applied to the first electrode 114 and the second electrode116, may have opposite signs and may have the same absolute value. TheDC power supply 112, applying a DC high voltage to the first electrode114 and the second electrode 116, may apply a level of 30 kV atatmospheric pressure. In this case, a vertical streamer is generated ina vertical direction in which the first electrode 114 and the secondelectrode 116 are connected (the direction of the central axis of thedielectric discharge tube 140), and a C-shaped streamer is generated onthe second electrode 116. When the second electrode 116 forms a perfectloop, first current flowing through the initial discharge induction coil120 may generate eddy current in the second electrode 116 and may heatthe second electrode 116. Therefore, the second electrode 116 may be cutwhile securing a sufficient area to suppress the eddy current or mayhave a slit in a vertical direction.

A gap between the first electrode 114 and the initial dischargeinduction coil 120 or a gap between the second electrode 116 and theinitial discharge induction coil 120 may be large enough to suppressparasitic discharge, caused by a high voltage at atmospheric pressure,and induction heating caused by an inducted magnetic field.Specifically, the gap between the first electrode 114 and the initialdischarge induction coil 120 or the gap between the second electrode 116and the initial discharge induction coil 120 may be several centimeters(cm) or more, in detail, 1 cm or more.

The RF power supply 150 may output RF power. The RF power supply 150 mayconvert commercial AC power into RF power and transmit the RF power to aload. For example, the RF power may have a frequency of several hundredsof KHz to several tens of MHz and a power of several kW or more. The RFpower supply 150 may include a rectifier, an inverter, and a controller.The rectifier may convert commercial AC power into DC power. Theinverter may receive the DC power and convert the received DC power intoRF power in response to switching signals of the controller. Thecontroller may control the switching signals to control a drivingfrequency and power. The RF power may perform impedance matching at afirst resonant frequency fa or a second resonant frequency fb bychanging a driving frequency. The first resonant frequency fa and thesecond resonant frequency fb may be spaced apart from each other by 0.2MHz or more. When the first resonant frequency fa is within 0.2 MHz atthe second resonant frequency fb, impedances in two current directionsare similar to each other, and thus, power switching may be unstable.The first resonant frequency fa may be higher than the second resonantfrequency fb.

A first detection sensor 152 may detect a current or a voltage flowingthrough the initial discharge induction coil 120. The second detectionsensor 154 may detect a current or a voltage flowing through the maindischarge induction coil module 103. The RF power supply 150 may detecta transition from a capacitively coupled mode to an inductively coupledmode using an output of the first detection sensor 152 and may change adriving frequency from the first resonant frequency to the secondresonant frequency.

Referring to FIG. 6 , a main discharge induction coil module 103includes a plurality of unit antennas, auxiliary capacitors 134 disposedbetween the plurality of unit antennas 132, and a first main capacitor133 a and a second main capacitor 133 b, respectively disposed at bothends of the antennas. A cross section of a coil, constituting the unitantenna 132, may have a rectangular shape. The unit antennas 132 may bedisposed clockwise at intervals of 90 degrees. Therefore, terminalselectrically connecting the unit antennas 132 may not interfere witheach other.

Referring to FIGS. 7 and 8 , a rectangular cross section may increase acontact area with the dielectric discharge tube 140 such that heatexchange efficiency may be improved to cool the dielectric dischargetube 140. When main discharge is performed, plasma may transfer energyto the dielectric discharge tube 140 to heat the dielectric dischargetube 140 to hundreds of degrees Celsius or more. An increase intemperature of the dielectric discharge tube 140 may cause modificationor damage of a material. A coolant flows inwardly of the unit antenna132 to cool the unit antenna 132. Since a coil having a circular crosssection is in line contact with the dielectric discharge tube 140, itmay be difficult to efficiently cool the dielectric discharge tube 140.A coil having a rectangular cross section increases in coolingefficiency through surface contact with the dielectric discharge tube140. To stably maintain contact with an internal coil of the unitantenna 132 and the dielectric discharge tube 140, the internal coil istightened to decrease in a radius. Experimentally, in the case of acircular cross-section coil, breakage of the dielectric discharge tube140 was found at RF power of 5 kW or more. However, in the case of arectangular cross-section coil, no breakage of the dielectric dischargetube 140 was found even at RF power of 8 kW.

The unit antenna 132 may include a first antenna 132 a disposed to be incontact with the dielectric discharge tube 140 on a placement planeperpendicular to the central axis of the dielectric discharge tube 140and forming a loop; a second antenna 132 b continuously connected to thefirst antenna 132 a, disposed to surround the first antenna 132 a, andforming a loop; and a third antenna 132 c continuously connected to thesecond antenna 132 b, disposed to surround the second antenna 132 b, andforming a loop.

The unit antenna 132 has a rectangular cross section, and the firstantenna 132 a adheres to the dielectric discharge tube 140 to cool thedielectric discharge tube 140. The first antenna 132 a and the secondantenna 132 b may be connected by the U-shaped first connector 32 a. Thesecond antenna 132 b and the third antenna 132 c may be connected by theU-shaped second connector 32 b.

A clamp 35 may be disposed to allow both ends of the first antenna 132 ato adhere to each other such that the first antenna 132 a is broughtinto contact with the dielectric discharge tube 140. The clamp 35 may bea cable tie.

The unit antenna 132 may include a plurality of turns disposed on thesame placement plane, and an insulating spacer 36 may insulate theplurality of turns and may have a “

” shape. The turns, each constituting the unit antenna 132, may beelectrically insulated by an insulating spacer 36 and may be maintainedat regular intervals. The insulating spacer 36 may insulate adjacentunit antennas 132. The insulating spacer may have a “

” shape, and the second antenna 132 b may be inserted into a recessedportion 36 a.

At least a portion of the first antenna 132 a may be molded using aceramic paste. A ceramic mold 37, surrounding at least a portion of thefirst antenna 132 a, may be in thermal contact with the dielectricdischarge tube 140. Therefore, when a coolant flows through the unitantenna 132, the cooled unit antenna 132 may cool the ceramic mold 37and the ceramic mold 37 may indirectly cool the dielectric dischargetube 140.

Capacitance 2C1 of the first main capacitor 133 a is the same ascapacitance of the second main capacitor 133 b. The capacitance 2C1 ofthe first main capacitor 133 a may be twice as high as capacitance C1 ofthe auxiliary capacitor 134.

The second resonant frequency fb may be given by the sum Lb ofinductances of the plurality of unit antennas 132 a and equivalentcapacitance C′b of the capacitors 133 a, 133 b, and 134.

A first voltage drop Va, induced to the initial discharge induction coil120 at the first resonant frequency fa, may be greater than a secondvoltage drop Vb induced to the unit antenna 132 a at the second resonantfrequency fb. It may be greater than. The second voltage drop Vb may beexpressed as a product of the second resonant frequency fb, secondcurrent Ib, and the inductance L1 of the unit antenna 132 a. The firstvoltage drop Va may be expressed as a product of the first resonantfrequency fa, first current Ia, and the inductance La of the initialdischarge induction coil.

The sum Lb of the inductances of the plurality of unit antennas may begreater than the inductance La of the initial discharge induction coil.

FIG. 10 is a circuit diagram of a DC power supply according to anotherexample embodiment of the present disclosure.

FIG. 11 is a circuit diagram illustrating a high-voltage pulse generatorin FIG. 10 .

Referring to FIGS. 10 and 11 , the DC power supply 112 may include anAC-DC converter 1120 converting commercial power into a DC voltage Vin;a high-voltage pulse generator 1122 receiving the DC voltage Vin togenerate a positive DC high-voltage pulse and a negative DC high-voltagepulse; and a controller 1124 controlling the high-voltage pulsegenerator.

The high-voltage pulse generator 1122 may include a first transformer1222 a including a primary coil receiving the DC voltage of the AC-DCconverter and a secondary coil generating a positive DC high-voltagepulse; a first power transistor 1222 b connected to the primary coil ofthe first transformer 1222 a; a second transformer 1222 c including aprimary coil receiving the DC voltage of the AC-DC converter and asecondary coil generating a negative DC high-voltage pulse; and a secondpower transistor 1222 d connected to the primary coil of the secondtransformer 1222 c. The controller 1124 may control gates of the firstpower transistor 1222 b and the second power transistor 1222 d. One endof the secondary coil of the first transformer 1222 a outputs a positiveDC high-voltage pulse, and the other end of the secondary coil of thefirst transformer 1222 a is grounded. One end of the secondary coil ofthe second transformer 1222 c outputs a negative DC high-voltage pulse,and the other end of the secondary coil of the second transformer 1222 cis grounded.

The DC voltage Vin may be a DC voltage of 12V to 24V. The controller1124 controls an ON time and a repetition frequency of the first powertransistor 1222 b and the second power transistor 1122 d insynchronization with each other. The DC high-voltage pulse may beseveral tens of kV, and the repetition frequency may be several tens ofkHz.

FIG. 12 is a cross-sectional view illustrating a main dischargeinduction coil module of an atmospheric-pressure plasma generatingapparatus according to another example embodiment of the presentdisclosure.

FIG. 13 is a plan view illustrating a disposition relationship of unitantennas of the main discharge induction coil module in FIG. 12 .

FIG. 14 is an equivalent circuit diagram illustrating an initialdischarge mode of the atmospheric-pressure plasma generating apparatusin FIG. 12 .

FIG. 15 is an equivalent circuit diagram illustrating a main dischargemode of the atmospheric-pressure plasma generating apparatus in FIG. 12.

FIG. 16 is a timing diagram illustrating an initial discharge mode and amain discharge mode of the atmospheric-pressure plasma generatingapparatus in FIG. 12 .

Referring to FIGS. 12 to 16 , the atmospheric-pressure plasma generatingapparatus 200 may include a dielectric discharge tube 140; an initialdischarge induction coil module 102 including an initial dischargeinduction coil 120 surrounding the dielectric cylindrical tube 140,having a plurality of turns, and generating initial discharge andinitial discharge capacitors 122 a and 122 b connected to the initialdischarge induction coil 120 in series to provide a first resonantfrequency fa; a first electrode 114 and a second electrode 116,respectively disposed above and below the initial discharge inductioncoil 120 to provide an initial discharge seed; a DC power supply 112applying a DC high voltage between the first electrode 114 and thesecond electrode 116; a main discharge induction coil module 203 havinga second resonant frequency fb and receiving the initial discharge,generated by the initial discharge induction coil module 102, togenerate main inductively coupled plasma; and an RF power supply 150providing RF power to the initial discharge induction coil module 102and the main discharge induction coil module 203 connected to each otherin parallel and changing a driving frequency.

The main discharge induction coil module 203 may include A plurality ofunit antennas 232 a to 232 d and 332 a to 332 e disposed to be spacedapart from the initial discharge induction coil 120, respectivelydisposed on a plurality of placement planes perpendicular to a centralaxis of the dielectric discharge tube 140, and connected to each otherin series; a first main capacitor 133 a and a second main capacitor 133b, respectively disposed on both ends of the unit antennas 232 a to 232d and 332 a to 332 e; and auxiliary capacitors 134 connected between theunit antennas 232 a to 232 d and 332 a to 332 e in series, respectively.

The RF power supply 150 induces initial discharge to the initialdischarge induction coil 120 at the first resonant frequency fa with thehelp of the DC high voltage. The RF power supply 150 changes the drivingfrequency from the first resonant frequency fa to a second resonantfrequency fb to perform main discharge.

The unit antennas 232 a to 232 d and 332 a to 332 e are disposed ondifferent placement planes and may be ten. The unit antennas 232 a to232 d and 332 a to 332 e are divided into a first group 232 a to 232 d,including five unit antennas, and a second group 332 a to 332 eincluding the other five unit antennas. The unit antennas, constitutingthe first group 232 a to 232 d, may be disposed at intervals of 72degrees in an azimuthal direction. The unit antennas, constituting thesecond groups 332 a to 332 e, may be disposed at intervals of 72 degreesin the azimuthal direction. Therefore, the unit antennas may notinterfere with each other to provide electrical connection betweenadjacent unit antennas.

Specifically, equivalent capacitance C′a of the initial dischargecapacitors 122 a and 122 b may be 260 pF, inductance La of the initialdischarge induction coil may be 8 uH, parasitic resistance of theinitial discharge induction coil Ra may be 0.5 ohm. The first resonantfrequency fa may be 3.3 MHz.

Inductance of the unit antenna may be 3.5 uH, and the sum of inductancesof the unit antenna may be 35 uH. Equivalent capacitance C′b of thecapacitors 133 a, 133 b, and 134, constituting the main dischargeinduction coil module 203, may be 156 pF. Parasitic resistance Rb of themain discharge induction coil module 203 may be 2.1 ohms. The secondresonant frequency fb may be 2.2 MHz.

Referring to FIG. 14 , in the initial discharging operation, the drivingfrequency may be a first resonant frequency of 3.3 MHz. In this case,first current Ia flowing through the initial discharge induction coilmodule 102 is 31.5 A, and second current Ib flowing through the maindischarge induction coil module 203 is 0.04 A. Therefore, a currentratio (a ratio of Ia to Ib) or an impedance ratio may be 800 to 1. Forexample, in the initial discharging operation, all currents may flow tothe initial discharging induction coil module 102 and may transitionfrom a capacitively coupled mode to an inductively coupled mode. Whenthe first current Ia, flowing through the initial discharge inductioncoil module 102, or a voltage is sensed to transition to the inductivelycoupled mode, the RF power supply changes the driving frequency into thesecond resonant frequency fb according to a control signal.

Referring to FIG. 15 , in the main discharge operation, the drivingfrequency may be 2.2 MHz, a second resonant frequency. In this case, thefirst current Ia flowing through the initial discharge induction coilmodule 102 is 0.5 A, and the second current Ib flowing through the maindischarge induction coil module 203 is 49.5 A. Therefore, a currentratio (a ratio of Ia to Ib) or an impedance ratio may be 1 to 100. Forexample, in the main discharge operation, all current flows to the maindischarge induction coil module 203. Thus, stable plasma is maintained.

In addition, in the main discharging operation, a maximum value V2 of apotential difference Vb applied to both ends of the unit antenna isabout 5.2 times smaller than a maximum value Vo of a potentialdifference Va applied to both ends of the initial discharging inductioncoil. Accordingly, thermal damage of the dielectric discharge tube 140may be eliminated during main discharge.

FIG. 17 is a conceptual diagram illustrating a plasma generatingapparatus according to FIG. 2A.

Referring to FIG. 17 , the plasma generating apparatus 100 may include adielectric discharge tube 140; a seed charge generator 105 generatingseed charges in the dielectric discharge tube 140; an initial dischargeinduction coil module 102 including an initial discharge induction coil120 surrounding the dielectric cylindrical tube 140 and receiving theseed charges to generate initial discharge and a first impedancematching network 122 connected to the initial discharge induction coil120 to provide a first resonant frequency; a main discharge inductioncoil module 103 including a plurality of unit antennas 132 disposed tobe spaced apart from the initial discharge induction coil 120,surrounding the dielectric cylindrical tube 140, and receiving theinitial discharge to generate a main inductively coupled plasma and asecond impedance matching network 133 connected to the plurality of unitantennas 132 to provide a second resonant frequency; and an RF powersupply 150 supplying power to the initial discharge induction coilmodule 102 and the main discharge induction coil module 103.

The seed charge generator 105 may include a first electrode 114, asecond electrode 116, and a DC power supply applying a DC high voltagebetween the first electrode 114 and the second electrode 116.

The DC power supply 112 may include an AC-DC converter 1120 convertingcommercial power into a DC voltage Vin; a high-voltage pulse generator1122 receiving the DC voltage Vin to generate a positive DC high-voltagepulse and a negative DC high-voltage pulse; and a controller 1124controlling the high-voltage pulse generator 1122.

The RF power supply 150 may include a rectifier 151, an inverter 156,and a control unit 158.

Referring to FIGS. 2A and 17 , the initial discharge capacitors 122 aand 122 b may be respectively disposed on both ends of the initialdischarge induction coil 120 to provide impedance matching for a loadwhile constituting a resonance circuit, and thus, may perform impedancematching. For example, the first impedance matching network 122 mayinclude the initial discharge capacitors 122 a and 122 b.

In addition, the first main capacitor 133 a and the second maincapacitor 133 b may be respectively disposed on both ends of the unitantennas, connected in series to perform main discharge, to provideimpedance matching for a load I while constituting a resonance circuit,and thus, may perform impedance matching. For example, the secondimpedance matching network 133 may include a first main capacitor 133 aand a second main capacitor 133 b.

A distance d2 between the initial discharge induction coil 120 and theunit antenna 132 of the main coil induction coil module may be longenough to protect the second electrode 116 causing seed charges to begenerated by a DC high voltage. To form a compact structure, the secondelectrode 116 disposed between the initial discharge induction coil 120and the unit antenna 132 of the main coil induction coil module 103needs to be removed. The seed charge generator 105 may generate seedcharges in various manners to stably generate the seed charges.

As an example, the seed charge generator 105 may include a pair ofelectrodes having a DC high voltage difference. One electrode may bedisposed on an external sidewall of the dielectric discharge tube 140,and the other electrode may be disposed on a central axis of thedielectric discharge tube 140. Therefore, a strong electric field may beapplied by a DC high-voltage pulse in a radial direction of thedielectric discharge tube 140 to generate seed charges. When the secondelectrode 116 disposed between the initial discharge induction coil 120and the unit antenna 132 of the main coil induction coil module isremoved, a plasma generating apparatus may have a compact structure. Inorder to stably generate the seed charges, a plurality of electrodes maybe disposed outside and/or inside of the dielectric discharge tube 140.Specifically, the first electrode 114 may receive a DC high voltage andmay be disposed to be in contact with the external sidewall of thedielectric discharge tube 140, and the second electrode may be groundedto be disposed inside of the dielectric discharge tube 140. The secondelectrode may be grounded and may perform a nozzle function to dischargean ignition gas and/or a process gas. Accordingly, an electric field maybe generated in the radial direction of the dielectric discharge tube140 by the DC high-voltage pulse, and the electric field may generateseed charges to induce initial discharge of the initial dischargeinduction coil module.

According to a modified embodiment, the seed charge generator 105 mayinclude a waveguide receiving a super-high frequency and radiating thesuper-high frequency through a slit. The super-high frequency, radiatedthrough the slit of the waveguide, may be transferred to the inside ofthe dielectric discharge tube 140 to generate seed charges at anatmospheric pressure.

FIG. 18 is a conceptual diagram illustrating a plasma generatingapparatus according to another example embodiment of the presentdisclosure.

Referring to FIG. 18 , a plasma generating apparatus 200 may include adielectric discharge tube 140; a seed charge generator 205 generatingseed charges in the dielectric discharge tube 140; an initial dischargeinduction coil module 102 including an initial discharge induction coil120 surrounding the dielectric discharge tube 140 and receiving the seedcharges to generate initial discharge and a first impedance matchingnetwork 122 connected to the initial discharge induction coil 120 toprovide a first resonant frequency; a main discharge induction coilmodule 103 including a plurality of unit antennas 132 disposed to spacedapart from the initial discharge induction coil 120, surrounding thedielectric discharge tube 140, and receiving the initial discharge togenerate main inductively coupled plasma and a second impedance matchingnetwork 133 connected to the unit antennas 132 to provide a secondresonant frequency; and an RF power supply 150 supplying power to theinitial discharge induction coil module 102 and the main dischargeinduction coil module 103.

The dielectric discharge tube 140 may be a cylindrical dielectric tube.

The seed charge generator 205 may include a first electrode 114 and asecond electrode 216 disposed on the dielectric discharge tube 140 toprovide seed charges; and a DC power supply 212 applying a DChigh-voltage pulse between the first electrode 114 and the secondelectrode 216. The first electrode 114 may have a plate or band shapeand may be disposed to be bent in contact with an external sidewall ofthe dielectric discharge tube 140. The second electrode 216 is disposedon a central axis of the dielectric discharge tube 140 and may beelectrically grounded. The second electrode 216 may have a cylindricalshape and may additionally perform a nozzle function to inject a gas.

The DC power supply 212 may output a DC high-voltage pulse VDC ofseveral kHz to several tens of kHz. The output DC voltage of the DCpower supply 112 may be several kV to several tens of kV. An electricfield E_ig may be generated in a radial direction of the dielectricdischarge tube 140 by the DC high-voltage pulse VDC, the electric fieldE_ig may generate seed charges in the state in which an ignition gas isinjected, and the seed charges may induce initial discharge of theignition gas of the initial discharge induction coil module 102. Theseed charge generator 105 may include a first electrode 114, a secondelectrode 116, and a DC power supply 112 applying a DC high voltagebetween the first electrode 114 and the second electrode 116.

The DC power supply 212 includes an AC-DC converter 2120 convertingcommercial power into a DC voltage Vin; a high-voltage pulse generator2122 receiving the DC voltage Vin to generate a positive DC high-voltagepulse and a negative DC high-voltage pulse; and a controller 2124controlling the high-voltage pulse generator 2122.

As an electrode disposed between the initial discharge induction coil120 and the unit antenna 132 of the main coil induction coil module isremoved, a compact structure may be formed. A distance d2 between theinitial discharge induction coil 120 and the unit antenna 132 of themain coil induction coil module may be maintained at 3 cm or less. Inaddition, a distance d1 between the initial discharge induction coil 120and the first electrode may be maintained at 3 cm or less.

The initial discharge induction coil module 102 includes the firstimpedance matching network 122 and the initial discharge induction coil120. The first impedance matching network 122 may include a pair ofinitial discharge capacitors 122 a and 122 b, respectively connected toboth ends of the initial discharge induction coil 120. The initialdischarge induction coil 120 may be in the form of a solenoid having amultilayer structure to increase inductance. The first resonantfrequency fa of the initial discharge induction coil module 102 mayrange from 4 MHz to 5 MHz, and current of several tens of amperes mayflow to the initial discharge induction coil module 102. The initialdischarge induction coil 120 generates initial discharge of a gas withthe help of the seed charges, and transitions from a capacitivelycoupled mode (or an E-mode) to an inductively coupled mode (or anH-mode). For example, the initial discharge plasma transitions from astreamer-type capacitively coupled mode to a bulk plasma-typeinductively coupled mode in which plasma is entirely generated inside ofthe dielectric discharge tube 140.

The main discharge induction coil module 103 may include a plurality ofunit antennas 132 disposed on a plurality of placement planesperpendicular to a central axis of the dielectric discharge tube andconnected to each other in series; auxiliary capacitors 134 connectedbetween adjacent unit antennas 132 in series; and the second impedancematching network 133 connected to the unit antennas 132 connected inseries. The main discharge induction coil module 103 may generate maininductively coupled plasma using the initial discharge of the gas.

The second impedance matching network 133 may include a first maincapacitor 133 a and a second main capacitor 133 b. The first maincapacitor 133 a and the second main capacitor 133 b is disposed on bothends of the unit antennas connected in series, respectively.

The main discharge induction coil module 103 has a second resonantfrequency fb and includes a second impedance matching network 133 toperform impedance matching with the second resonant frequency fb. Theunit antennas 132 may have at least one turn in the same plane. The unitantennas 132 are disposed on different placement planes, and adjacentunit antennas are connected to each other in series through an auxiliarycapacitor 134.

The RF power supply 150 may include a rectifier 151 convertingcommercial AC power into DC power; an inverter 156 receiving the DCpower and converting the received DC power into RF power in response toswitching signals from the controller 158; and a controller 158controlling the switching signals to control the driving frequency andpower. The RF power supply 150 may operate at the first resonantfrequency fa during initial discharge, and may operate at the secondresonant frequency fb when main inductively coupled plasma is generated.The RF power supply 150 may be a variable frequency power supply. The RFpower supply 150 may change an ignition gas into a process gas tomaintain the main inductively coupled plasma when the main inductivelycoupled plasma is generated.

The rectifier 151 may convert an output of commercial AC power into DCpower. The rectifier 151 may supply DC power between a ground node GNDand a power supply node VP. A capacitor may be connected between theground node GND and the power supply node VP to discharge an ACcomponent to the ground node GND.

The inverter 156 may receive a switching signal from the controller 158to convert DC power into AC power in response to the switching signals.The controller 158 may control a switching signal to adjust the amountof power and a driving frequency provided from an inverter to a load.

In the case of a single RF power supply, the first resonant frequency faand the second resonant frequency fb should be sufficiently spaced apartfrom each other by 0.2 MHz or more. However, it may be difficult for theRF power to provide a stable output for a wide frequency variable range.In particular, the initial discharge is advantageous as a drivingfrequency is increased and a large amount of current flows. Therefore,both ends of the initial discharge induction coil may be maintained at ahigh potential difference by high current and high inductance to causecapacitively coupled mode discharge at the first resonant frequency fa.The main inductively coupled plasma requires high power of several kW ormore and low voltage drop of a unit antenna. A high-power RF powersupply of several kW or more may operate at the second resonantfrequency fb lower than the first resonant frequency fa. Accordingly,the first RF power operating at the first resonant frequency and thesecond RF power operating at the second resonant frequency havedifferent characteristics and may be separated from each other.

FIG. 19 is a conceptual diagram illustrating a plasma generatingapparatus according to another example embodiment of the presentdisclosure.

FIG. 20 is a conceptual diagram illustrating discharge of the plasmagenerating apparatus in FIG. 19 .

FIG. 21 is a timing diagram of signals in FIG. 19 .

FIG. 22 is a flowchart illustrating a method for operating the plasmagenerating apparatus in FIG. 19 .

Referring to FIGS. 19 to 22 , a plasma generating apparatus 300 mayinclude a dielectric discharge tube 140; a seed charge generator 205generating seed charges in the dielectric discharge tube 140; an initialdischarge induction coil module 102 including an initial dischargeinduction coil 120 surrounding the dielectric cylindrical tube 140 andreceiving the seed charges to generate an initial discharge and a firstimpedance matching network 122 connected to the initial dischargeinduction coil 120 to provide a first resonant frequency; a maindischarge induction coil 103 including a plurality of unit antennas 132disposed to be spaced apart from the initial discharge induction coil120, surrounding the dielectric discharge tube 140, and receiving theinitial discharge to generate main inductively coupled plasma and asecond impedance matching network 133 connected to the unit antennas 132to provide a second resonant frequency; and an RF power supply 350supplying power to the initial discharge induction coil module 102 andthe main discharge induction coil module 103.

The first RF power supply 350 a, inducing initial discharge, may bedesigned to drive high current of tens of amperes or more at a firstresonant frequency fa of several MHz or more. The second RF power supply350 b, inducing the main discharge plasma, may be designed to providehigh power of several kW or more at a second resonant frequency fb ofseveral MHz or less, in detail, 400 kHz to 4 MHz. Specifically, thefirst RF power supply 350 a may be implemented through a half-bridgeinverter circuit, and the second RF power supply 350 b may beimplemented through a full-bridge inverter circuit. The first RF powersupply 350 a may be controlled to operate at a fixed first resonantfrequency fa. The second RF power supply 350 b may control a drivingfrequency to adjust the amount of power or impedance to operate at afrequency near a second resonant frequency fb.

The RF power supply 350 may include a first RF power supply 350 asupplying AC power to the initial discharge induction coil module 102and operating at the first resonant frequency fa; and a second RF powersupply 350 b supplying AC power to the main discharge induction coilmodule 103 and operating at the second resonant frequency fb.

The first RF power supply 350 a may include a first rectifier 351 aconverting AC power to DC power; a first inverter 356 a receiving DCpower from the first rectifier 351 a to supply AC power having the firstresonance frequency fa to the initial discharge induction coil module102; and a first controller 358 a controlling an output of the firstinverter 356 a. The first RF power supply 350 a may operate at the firstresonant frequency fa.

The second RF power supply 350 b may includes: a second rectifier 351 bconverting AC power into DC power; a second inverter 356 b receiving DCpower from the second rectifier 351 b to supply AC power having thesecond resonant frequency fb to the main discharge induction coil module103; and a second controller 358 b controlling an output of the secondinverter 356 b. The second RF power supply 350 b may operate, whilevarying, around the second resonant frequency fb.

A method for operating a plasma generating apparatus according to anexample embodiment may include injecting a first gas into a dielectricdischarge tube 140 (S210); providing seed charges to an inside of thedielectric discharge tube 140 using the first gas (S220); performinginitial discharge of the first gas from the seed charges with AC powerof the first resonant frequency using the initial discharge inductioncoil 120 and the first impedance matching network 122 connected to theinitial discharge induction coil 120 (S230); and generate maininductively coupled plasma of the first gas from the initial dischargewith AC power of the second resonant frequency fb, different from thefirst resonant frequency fa, using a plurality of unit antennas 132 anda second impedance matching network 133 (S260).

In the operation of injecting the first gas into the dielectricdischarge tube 140 (S210), the first gas may be injected to an upperportion of the dielectric discharge tube 140 through the secondelectrode 216 performing a nozzle function. A pressure of the dielectricdischarge tube 140 may be several Torr or more, in detail, anatmospheric pressure or more. The first gas may be an argon gas, anitrogen gas, a hydrogen-containing gas, or a carbon dioxide gas, whichare advantageous for ignition, or combinations thereof.

In the operation of providing seed charges using the first gas in thedielectric discharge tube 140 (S220), the seed charges may be formedusing the seed charge generator 205. For example, the first electrode114 may be attached to an external sidewall of the dielectric dischargetube 140, and the second electrode 216 may be inserted into a centralaxis of the dielectric discharge tube 140 to face the first electrode114. The second electrode 216 may be grounded and may perform a nozzlefunction to inject a first gas or a second gas. In the state in whichthe second electrode 216 is grounded, the first electrode 114 maygenerate seed charges using a DC high-voltage pulse VDC. The secondelectrode 216 may act as a cathode, and the first electrode 114 may actas an anode. The DC high-voltage pulse VDC may have a pulse frequency ofseveral tens of kHz and a voltage of several tens of kV.

In the operation of performing initial discharge of the first gas fromthe seed charges (S230), AC power PO1 of the first resonant frequency famay be supplied to the initial discharge induction coil module 102. Whenthe AC power PO1 of the first resonant frequency is applied to theinitial discharge induction coil module 102 while a DC high-voltagepulse is applied, both ends of the initial discharge induction coil 120have high inductance due to a high potential difference. A verticalelectric field E_z may be generated in a direction of the central axisof the dielectric discharge tube 140. The vertical electric field E_zmay generate capacitively coupled mode (or E-mode) plasma. Thecapacitively coupled mode may transition to an inductively coupled mode(or an H mode). Accordingly, current Ia flowing through the initialdischarge induction coil 120 may be decreased due to an increase inactual resistance of initial discharge plasma, a load, and the AC powerPO1 of the first resonant frequency may be increased due to the increasein the actual resistance of the initial discharge plasma, a load. Themode transition may be detected by monitoring the AC power PO1 or thecurrent Ia at the first resonant frequency. The detection of the currentIa may be performed using a first detection sensor 152 disposed on anoutput terminal of the first RF power. The first detection sensor 152may be a Hall sensor sensing current. Alternatively, the first detectionsensor 152 may be disposed on an input terminal of the first inverter356 a to detect input current of the first inverter 356 a and to monitorAC power using information of the DC power and the input current.

After the mode transition or even before the mode transition of theinitial discharge, the DC high-voltage pulse VDC may be removed to stopsupplying the seed charges (S240).

Preliminary main inductively coupled plasma of the first gas may begenerated from the initial discharge with the AC power near the secondresonant frequency fb using the plurality of unit antennas 132 and thesecond impedance matching network 133 (S250).

The main discharge induction coil module 103 may include the pluralityof unit antennas 132, an auxiliary capacitor 134 connected betweenadjacent unit antennas in series, and the second impedance matchingnetwork 133. Similarly to the initial discharge induction coil module,the main discharge induction coil module 103 may have a capacitivelycoupled mode (or an E-mode) and an inductively coupled mode (or anH-mode). The second RF power supply 350 b may output AC power PO2.

The second RF power supply 350 b may initially supply the AC power P1 ofan initial frequency near the second resonant frequency fb such that themain discharge may stably transition to the inductively coupled mode (orthe H-mode). The initial frequency may be several tens to severalhundreds of kHz greater than the second resonant frequency fb.Accordingly, a potential difference applied to both ends of the unitantenna of the main discharge induction coil module 103 at the initialfrequency may be greater than a potential difference applied at thesecond resonant frequency fb. A potential difference, applied to bothends of the unit antenna at the initial frequency, may stably generatepreliminary main inductively coupled plasma using charges generated bythe initial discharge. The AC power P1 of the initial frequency may besupplied after or at the same time after the E-mode transition of theinitial discharge.

In the operation of generating the main inductively coupled plasma ofthe first gas (S260), the second RF power supply 350 b may supply the ACpower P2 of the second resonant frequency fb to the main dischargeinduction coil module 103. For example, the second RF power supply 350 bmay change a frequency to supply the AC power P2 of the second resonantfrequency fb to the main discharge induction coil module 103.Accordingly, the AC power P2 of the second RF power supply 350 b may beimpedance-matched to be increased, and the main discharge induction coilmodule 103 may stably operate the inductively coupled mode (or theH-mode). As the frequency changes to the second resonant frequency, thecurrent Ib flowing through the main discharge induction coil module 103may be increased due to impedance matching. Therefore, stable maininductively coupled plasma using the first gas is maintained. Thedetection of the current Ib may be performed using a second detectionsensor 154 disposed on an output terminal of the second RF power. Thesecond detection sensor 154 may be a Hall sensor sensing current.Alternatively, the second detection sensor 154 may be disposed on theinput terminal of the second inverter 356 b to detect the input currentof the second inverter 356 b and to monitor AC power using informationof the DC power and the input current.

Then, when the main inductively coupled plasma is generated, AC power ofthe first resonant frequency fa may be interrupted (S270). Theinterruption of the AC power of the first resonant frequency fb,provided to the initial discharge induction coil module, may beperformed simultaneously with or immediately before the change to thesecond resonant frequency. The current Ib or the AC power P2 of thesecond resonant frequency fb may be detected to determine whether themain inductively coupled plasma is generated.

The first gas may be an ignition gas advantageous for igniting. Thefirst gas may be argon, carbon dioxide, or nitrogen. On the other hand,the second gas may be a process gas which is difficult to ignite and mayinclude a fluorine-containing gas or the like. Therefore, when a gaswhich is difficult to initially ignite is used, the gas may bedischarged with a first gas which easily ignites and may be replacedwith a second gas (S280). The main inductively coupled plasma of thefirst gas may change to the main inductively coupled plasma of thesecond gas while maintaining substantially the same pressure.Conventionally, actual plasma resistance of the fluorine-containing gasmay be lower than actual resistance of an argon gas. Therefore, when thegas is replaced with the second gas, the current Ib flowing through themain discharge induction coil module 103 may be increased, and the ACpower P3 of the second resonant frequency fb may be increased.

FIG. 23 is a conceptual diagram illustrating a plasma generatingapparatus according to another example embodiment of the presentdisclosure.

Referring to FIG. 23 , a plasma generating apparatus 400 may include adielectric discharge tube 140; a seed charge generator 205 disposed onthe dielectric discharge tube 140 to generate seed charges in thedielectric discharge tube 140; an initial discharge induction coilmodule 102 including an initial discharge induction coil 120 surroundingthe dielectric discharge tube 140 and receiving the seed charges togenerate initial discharge and a first impedance matching network 122connected to the initial discharge induction coil 120 to provide a firstresonant frequency fa; a main discharge induction coil module 103including at least one unit antenna 132 disposed to be spaced apart fromthe initial discharge induction coil 120, surrounding the dielectricdischarge tube 140, receiving the initial discharge to generate maininductively coupled plasma and a second impedance matching network 133connected to the unit antenna 132 to provide a second resonant frequencyfb; and an RF power supply 450 supplying power to the initial dischargeinduction coil module 102 and the main discharge induction coil module103.

The RF power supply 450 includes: a rectifier 151 converting AC powerinto DC power; a first RF power supply 450 a receiving DC power from therectifier 151 to provide AC power to the initial discharge inductioncoil module 102 and operating at the first resonant frequency fa; and asecond RF power supply 450 b receiving DC power from the rectifier 151to provide AC power to the main discharge induction coil module 103 andoperating at the second resonant frequency fb.

The first RF power supply 450 a includes: a first inverter 456 areceiving DC power from the rectifier 151 and converting the received DCpower into first AC power of the first resonant frequency fa; and afirst control unit 458 a controlling the first inverter 456 a.

The second RF power supply 450 b includes: a second inverter 456 breceiving DC power from the rectifier 151 and converting the received DCpower into AC power of the second resonant frequency fb; and a secondcontrol unit 458 b controlling the second inverter.

The rectifier of the first RF power supply 450 a and the rectifier ofthe second RF power supply 450 b may be commonly used. Since a timerequired to simultaneously operate the first RF power 450 a and thesecond RF power 450 b is very short, no issue occurs in the operation ofthe second RF power supply 450 b.

FIGS. 24 and 25 illustrate an initial discharge induction coil moduleconnected to a first RF power supply according to an example embodimentof the present disclosure.

Referring to FIGS. 24 and 25 , a first RF power supply 450 a has apositive output and a negative output, and is connected to an initialignition induction coil 120 through a first impedance matching network122. The initial ignition induction coil 120 has high inductance of 8uH. The first impedance matching network 122 may include at least oneinitial discharge capacitor. A first resonant frequency fa may be givenby the inductance La of the initial discharge induction coil 120connected to equivalent capacitance C′a of the initial dischargecapacitor.

FIG. 26 illustrates an initial discharge induction coil module connectedto a first RF power supply according to another example embodiment ofthe present disclosure.

Referring to FIG. 26 , a first RF power supply 450 a has a positiveoutput and a negative output, and is connected to an initial ignitioninduction coil 120 through a first impedance matching network 122. Theinitial ignition induction coil 120 has high inductance of 8 uH. Thefirst impedance matching network 122 may include a pair of initialdischarge capacitors 122 a and 122 b.

The pair of initial discharge capacitors 122 a and 122 b are connectedto both ends of the initial discharge induction coil, respectively. Thepositive output of the first RF power supply 450 a is connected to afirst initial discharge capacitor 122 a, and the negative output of thefirst RF power supply 450 a is connected to a second initial dischargecapacitor 122 b. A first resonant frequency fa may be defined byequivalent capacitance C′a of the pair of initial discharge capacitors122 a and 122 b and inductance La of the initial discharge inductioncoil 120. The first initial discharge capacitor 122 a and the secondinitial discharge capacitor 122 b may have the same capacitance Ca, andthe equivalent capacitance C′a may be Ca/2. The first resonant frequencyfa may be given by the inductance La of the initial discharge inductioncoil 120 connected to the equivalent capacitance C′a of the initialdischarge capacitor in series.

FIG. 27 illustrates an initial discharge induction coil module connectedto a first RF power according to another example embodiment of thepresent disclosure.

Referring to FIG. 27 , a first RF power supply 450 a has a positiveoutput and a negative output, and is connected to an initial ignitioninduction coil 120 through a first impedance matching network 222. Thefirst impedance matching network 222 may include a transformer 222 c,connected to an output terminal of the first RF power supply 450 a, anda pair of initial discharge capacitors 222 a and 222 b, respectivelyconnected to both ends of a initial discharge induction coil 120 inseries. A primary coil of the transformer 222 c may be connected to theoutput terminal of the first RF power supply 450 a, and a secondary coilof the transformer 222 c may be connected to both ends of an initialdischarge induction coil and the pair of initial discharge capacitors220 a and 220 b connected in series. Impedance at a side of a load maybe converted depending on a turn ratio (N:1) of the transformer 222 c.Capacitance of the first initial discharge capacitor and capacitance Caof the first initial discharge capacitor may be the same. A firstresonant frequency may be given by inductance La of the initialdischarge induction coil 120 connected to equivalent capacitance C′a ofthe initial discharge capacitor in series.

FIG. 28 illustrates an initial discharge induction coil module connectedto a first RF power according to another example embodiment of thepresent disclosure.

Referring to FIG. 28 , a first RF power supply 450 a has a positiveoutput and a negative output, and is connected to an initial ignitioninduction coil 120 through a first impedance matching network 322.

The first impedance matching network 322 may include a first initialdischarge capacitor 322 a connected to an initial discharge inductioncoil 120 in parallel; and a first initial discharge capacitor 322 a anda second initial discharge capacitor 322 b and a third initial dischargecapacitor 322 c connected to each other in parallel. The second initialdischarge capacitor 322 b and the third initial discharge capacitor 322c are connected to both ends of an initial discharge induction coil,respectively. Equivalent capacitance of the first to third initialdischarge capacitors 322 a, 322 b, and 322 c may be C′a=1/2 Ca.Capacitance of the first initial discharge capacitor 322 a may be0.5×(1−k)×Ca. Capacitance of the second and third initial dischargecapacitors 322 b and 322 c may be k×Ca. Here, 0<k<1 may be in the range.Ca is the capacitance of the initial discharge capacitor described inFIG. 26 . A first resonant frequency may be given by inductance La ofthe initial discharge induction coil 120 connected to the equivalentcapacitance C′a of the initial discharge capacitor in series.

FIG. 29 illustrates a main discharge induction coil module connected toa second RF power supply according to another example embodiment of thepresent disclosure.

Referring to FIG. 29 , a main discharge induction coil module 103includes a plurality of unit antennas 132 connected to each other inseries, an auxiliary capacitor 134 connected between adjacent unitantennas in series, and a second impedance matching network 133connected to a plurality of unit antennas connected in series. Theplurality of unit antennas 132 may be disposed on a plurality ofplacement planes, perpendicular to a central axis of a dielectricdischarge tube, and may be connected to each other in series. Theauxiliary capacitors 134 may be connected between adjacent unit antennasin series. The second impedance matching network 133 may include a firstmain capacitor 133 a and a second main capacitor 133 b, respectivelyconnected to both ends of the unit antennas connected in series.

A second resonant frequency fb may be given by the sum of inductances ofthe unit antennas and equivalent capacitances of the capacitors. Whencapacitance of the auxiliary capacitor 134 is C1, capacitance of each ofthe first main capacitor 133 a and the second main capacitor 133 b maybe 2C1. Inductance of each of the unit antennas may be L1.

FIG. 30 is a circuit diagram of a full-bridge inverter used in a firstinverter or a second inverter.

Inverters 456 a and 456 b receive DC power from a power supply node VPand a ground node GND. The inverters 456 a and 456 b receive switchingsignals A, B, C, and D from controllers 458 a and 458 b. The inverters456 a and 456 b may convert DC power into AC power in response to theswitching signals A, B, C, and D.

First and second transistors TR1 and TR2 may be connected between thepower supply node VP and the ground node GND in series. A first diode D1may be connected to a first transistor TR1 in parallel, and a seconddiode D2 may be connected to a second transistor TR2 in parallel. Afirst capacitor C1 may be connected to the first transistor TR1 inparallel, and a second capacitor C2 may be connected to the secondtransistor TR in parallel.

Third and fourth transistors TR1 and TR2 may be connected between thepower supply node VP and the ground node GND in series. A third diode D3may be connected to a third transistor TR3 in parallel, and a fourthdiode D4 may be connected to the fourth transistor TR4 in parallel. Athird capacitor C3 may be connected to the third transistor TR3 inparallel, and a fourth capacitor C4 may be connected to the fourthtransistor TR4 in parallel.

When a driving frequency of an output voltage VO is adjusted, a phasedifference between an output voltage and output current may be adjusted.

FIG. 31 is a circuit diagram of a half-bridge inverter according to anexample embodiment of the present disclosure.

Referring to FIG. 31 , inverters 456 a and 456 b receive DC power from apower supply node VP and a ground node GND. The inverters 456 a and 456b receive switching signals A and B from controllers 458 a and 458 b.The inverters 456 a and 456 b may convert DC power into AC power inresponse to switching signals A and B.

First and second transistors TR1 and TR2 may be connected between thepower supply node VP and the ground node GND in series. A first diode D1may be connected to the first transistor TR1 in parallel, and the seconddiode D2 may be connected to the second transistor TR2 in parallel. Afirst capacitor C1 may be connected to the first transistor TR1 inparallel, and the second capacitor C2 may be connected to the secondtransistor C2 in parallel.

A first voltage divider capacitor C11 and a second voltage dividercapacitor C22 may be connected between the power supply node VP and theground node GND in series.

When a driving frequency of an output voltage VO is adjusted, a phasedifference between the output voltage VO and output current may beadjusted.

FIG. 32 is a conceptual diagram illustrating a seed charge generatoraccording to another example embodiment of the present disclosure.

Referring to FIG. 32 , a seed charge generator 305 includes a firstelectrode 314 and a second electrode 316 disposed on a dielectricdischarge tube 140 to provide seed charges; and a DC power supply 312applying a DC high voltage between the first electrode 314 and thesecond electrode 316.

The DC power supply 312 includes an AC-DC converter 3120 convertingcommercial AC power into a DC voltage Vin; high-voltage pulse generators3122 a and 3122 b receiving the DC voltage Vin to generate at least onehigh-voltage pulse of a positive DC high-voltage pulse and a negative DChigh-voltage pulse; and controllers 3124 a and 3124 b controlling thehigh-voltage pulse generator. The high-voltage pulse generators 3122 aand 3122 b may include: a first high-voltage pulse generator 3122 areceiving the DC voltage to generate a first high-voltage pulse; and asecond high-voltage pulse generator 3122 b receiving the DC voltage togenerate a second high-voltage pulse.

The controllers 3124 a and 3124 b, controlling the high-voltage pulsegenerator, may include a first controller 3124 a controlling the firsthigh-voltage pulse generator 3122 a and a second controller 3124 bcontrolling the second high-voltage pulse generator 3122 b. A firsthigh-voltage pulse may be applied to the first electrode 314, and asecond high-voltage pulse may be applied to the second electrode 316.The first electrode 314 and the second electrode 316 may be disposed tobe spaced apart from each other on an external sidewall of thedielectric discharge tube 140. The first high-voltage pulse and thesecond high-voltage pulse may have polarities opposite to each other.

Returning to FIGS. 10 and 11 , the DC power supply 112, applying a DChigh voltage, may generate a positive high-voltage pulse and/or anegative high-voltage pulses. The negative high-voltage pulse and thepositive high-voltage pulse may be applied to the first electrode 314and the second electrode 316, respectively.

FIG. 33 is a conceptual diagram illustrating a negative high-voltagepulse generator according to an example embodiment of the presentdisclosure.

Referring to FIG. 33 , a high-voltage pulse generator 2122 includes atransformer 2122 a including a primary coil receiving a DC voltage Vinof an AC-DC converter 2120 and a secondary coil generating a negative DChigh voltage pulse; an inductor L connected to the primary coil 2122 aof the transformer 2122 a in parallel; a power transistor 2122 bconnected to the primary coil of the transformer 2122 a in series andhaving an end grounded; a resistor R connected to the power transistor2122 b in parallel; a capacitor C connected to the power transistor 2122b in parallel; and a diode D disposed between the other end of the powertransistor 2122 b and the resistor R and the capacitor C connected inparallel. A controller 2124 controls a gate of the power transistor 2122b.

One end of the secondary coil of the transformer 2122 a may output anegative DC high-voltage pulse, and the other end of the secondary coilof the transformer 2122 a may be grounded.

FIG. 34 is a conceptual diagram illustrating a negative high-voltagepulse generator according to another example embodiment of the presentdisclosure.

Referring to FIG. 34 , a voltage pulse generator 2122′ includes atransformer 2122 a including a primary coil receiving a DC voltage Vinof an AC-DC converter 2120 and a secondary coil generating a negative DChigh-voltage pulse; an inductor L connected to the primary coil of thetransformer 2122 a in parallel; and a power transistor 2122 b connectedbetween a ground and the primary coil of the transformer 2122 a inseries. A controller 2124 may control a gate of the power transistor2122, and one end of the secondary coil of the transformer 2122 a mayoutput a negative DC high-voltage pulse, and the other end of thesecondary coil of the transformer 2122 a may be grounded.

FIG. 35 is a conceptual diagram illustrating a negative high-voltagepulse generator according to another example embodiment of the presentdisclosure.

Referring to FIG. 35 , a high-voltage pulse generator 4122 includes atransformer 4122 a including a primary coil receiving a DC voltage of anAC-DC converter 2120 and a secondary coil generating a positive DChigh-voltage pulse; an inductor L connected to the primary coil of thetransformer 4122 a in parallel; a power transistor 4122 b connectedbetween a ground and the primary coil of the transformer 4122 a inseries; a resistor R and a capacitor C having one end connected to theDC voltage Vin of the AC-DC converter 2120 and connected to each otherin parallel; and a diode D having one end connected between the powertransistor 4122 b and the primary coil and the other end connected tothe other end of the resistor R and the capacitor C connected to eachother in parallel. A controller 4124 controls a gate of the powertransistor 412 b, and one end of the secondary coil of the transformer4122 a may output a negative DC high-voltage pulse, and the other end ofthe secondary coil of the transformer 4122 a may be grounded.

FIG. 36 is a conceptual diagram illustrating a positive high-voltagepulse generator according to another example embodiment of the presentdisclosure.

Referring to FIG. 36 , a high-voltage pulse generator 5122 includes atransformer 5122 a including a primary coil receiving a DC voltage Vinof an AC-DC converter 2120 and a secondary coil generating a positive DChigh-voltage pulse; an inductor L connected to the primary coil of thetransformer 5122 a in parallel; a power transistor 5122 b connectedbetween a ground and the primary coil of the transformer 5122 a inseries; a resistor R connected to the power transistor 5122 b inparallel; a capacitor C connected to the power transistor 5122 b inparallel; and a diode D disposed between the other end of the powertransistor 5122 b and the resistor R and the capacitor C connected toeach other in parallel. The primary coil and the secondary coil have aphase difference of 180 degrees, the controller 5124 controls a gate ofthe power transistor 5122 b, and one end of the secondary coil of thetransformer 5122 a outputs a positive DC high-voltage pulse and theother end of the secondary coil of the transformer 5122 a is grounded.

FIG. 37 is a plan view of a unit antenna of a main discharge inductioncoil module according to another example embodiment of the presentdisclosure.

Referring to FIG. 37 , a unit antenna 132′ may include a first antennadisposed to be in contact with the dielectric discharge tube 140 on aplacement plane, perpendicular to a central axis of a dielectricdischarge tube, and forming a loop 132 a and a second antenna 132 bcontinuously connected to the first antenna 132 a, disposed to surroundthe first antenna, and forming a loop. The unit antenna 132′ has arectangular cross section, and the first antenna 132 a is in closecontact with the dielectric discharge tube to cool the dielectricdischarge tube.

As described above, an atmospheric-pressure plasma generating apparatusaccording to an example embodiment may stably generate plasma atatmospheric pressure or higher pressure using an electrode forgenerating seeds, an initial discharge induction coil advantageous forignition, and a main discharge induction coil module advantageous formaintaining discharge.

While example embodiments have been shown and described above, it willbe apparent to those skilled in the art that modifications andvariations could be made without departing from the scope of the presentinventive concept as defined by the appended claims.

1. A plasma generating apparatus, comprising: a dielectric tubeconfigured to provide a space for plasma and comprising a first inlet atone end of the dielectric tube and an outlet at the other end of thedielectric tube; a first antenna module surrounding an outer side wallof the dielectric tube and comprising two terminals; two firstcapacitors connected to the first antenna module, wherein one firstcapacitor is serially connected to one terminal of the first antennamodule, and wherein the other first capacitor is serially connected tothe other terminal of the first antenna module; a second antenna modulesurrounding the outer side wall of the dielectric tube and comprisingtwo terminals, wherein the first antenna module is closer to the firstinlet than the second antenna module and the second antenna module iscloser to the outlet than the first antenna module, and wherein aninductance of the first antenna module is smaller than an inductance ofthe second antenna module; two second capacitors connected to the secondantenna module, wherein one second capacitor is serially connected toone terminal of the second antenna module, and wherein the other secondcapacitor is serially connected to the other terminal of the secondantenna module; and a RF generator configured to provide RF power withthe first antenna module or the second antenna module, wherein the RFpower is provided to the first antenna module via the two firstcapacitors and is provided to the second antenna module via the twosecond capacitors, wherein the RF generator is configured to providefirst RF power of first frequency to the first antenna module via thetwo first capacitors and provide second RF power of second frequency tothe second antenna module via the two second capacitors, and wherein thefirst frequency is different from the second frequency.
 2. The plasmagenerating apparatus of claim 1, wherein the second antenna modulecomprises a plurality of layer-antenna and a plurality of inter-layerscapacitors.
 3. The plasma generating apparatus of claim 2, wherein theplurality of layer-antenna and the plurality of inter-layers capacitorsare electrically connected in series.
 4. The plasma generating apparatusof claim 2, wherein each of the plurality of layer-antenna comprises atleast two turn-antenna, and wherein each of the plurality ofinter-layers capacitor electrically connects one layer-antenna toanother adjacent layer-antenna in series.
 5. The plasma generatingapparatus of claim 4, wherein an inductance of the each of the pluralityof layer-antenna is smaller than an inductance of the first antennamodule, and wherein an inductance of the second antenna module is lagerthan the inductance of the first antenna module.
 6. The plasmagenerating apparatus of claim 1, further comprising: a sensor configuredto detect a current flowing between the one terminal of the firstantenna and the other terminal of the first antenna module or a voltagebetween the one terminal of the first antenna and the other terminal ofthe first antenna module.
 7. The plasma generating apparatus of claim 6,wherein the RF generator configured to: receive a detection result fromthe sensor, and determine while providing the first RF power to thefirst antenna module, determine a time of providing the second RF powerto the second antenna module according to the detection result, andstart to provide the second RF power to the second antenna module basedon the determined time.
 8. The plasma generating apparatus of claim 1,further comprising a second inlet located between the first inlet andthe outlet.
 9. The plasma generating apparatus of claim 1, wherein thefirst frequency is larger than the second frequency.
 10. The plasmagenerating apparatus of claim 1, wherein potential difference betweenthe one terminal and the other terminal of the first antenna module whenthe first RF power is provided to the first antenna module is largerthan potential difference between the one terminal and the otherterminal of the second antenna module when the second RF power isprovided to the second antenna module.